Abnormal temperature dependence of band-gap energies observed in (InAs)/(GaAs) and (InP)/(GaP) superlattices with strong lateral composition modulation

An abnormal variation of the band-gap energy with temperature was observed in both the (InAs)(2.2)/(GaAs)(2) and (InP)(2)/(GaP)(2) short-period-superl attice (SPS) structures. Strong lateral composition modulation induced two horizontally adjacent regions with different In content in the SPS regions. Due to the difference of thermal expansion coefficients among the substrat e and the two adjacent regions in the SPS structures, it is proposed that a thermal strain has been generated and accommodated by altering the lattice constant in the growth direction. The magnitude of lattice variation depen ds on the relative thermal expansion and compressibility of the two adjacen t materials. The net modification of the lattice thermal expansion in the I n-rich region results in the abnormal variation of band-gap energies with t emperature. (C) 2000 American Institute of Physics. [S0021-8979(00)08301-8] .